He resigned from the post after four years, in protest against cuts in social service, thus becoming spokesperson for the party's left. This was reinforced when he later opposed party leader Hugh Gaitskell's stand against unilateral nuclear disarmament.

He became Labour party leader and opposition leader in 1963 and then prime minister in 1964 with a four-seat majority, which was increased dramatically in the 1966 election. During his time in office, he negotiated British membership of the EC, tried (and failed) to reach a settlement with Ian Smith's apartheid-esque regime in Rhodesia, and enacted economic reforms to address the growing crises in the British economy. These reforms seemed to be having an effect, and Wilson called a June1970 general election on the back of them. However, he was unexpectedly defeated by Edward Heath's Tories. Then he won in 1974 and was again prime minister. His ministry proceeded to be hindered by economic problems and saddled with the issue of Britain's admission to the European Community. However, in 1975 Wilson achieved one of his major successes by silencing his left-wing critics and confirming Britain's membership in the EEC via a referendum. However, Britain's economic problems continued, causing Wilson to resign in 1976, succeeded by James Callaghan, who was in turn crushed underneath Thatcher's jackboot. He became peer in the House of Lords in 1983.